[QUOTE=markr;324131]P-1 found a factor in stage #2, B1=25000000, B2=1000000000, E=12.
M428899 has a factor: 125121243653506108640827021803878584977256889
45 decimal digits, 147 bits
k = 2^2 * 73 * 83 * 3571 * 3923 * 12583 * 13513 * 37691 * 84307 * 795132769

My first reaction was "nice, a composite factor". I was a bit stunned when it wasn't.[/QUOTE]

Not the record for largest B2(no B-S)/B2(actual), but that's still massive. :smile:

James, is there a simple "largest P-1 factors" list on your site?

[QUOTE=Dubslow;324142]Not the record for largest B2(no B-S)/B2(actual), but that's still massive. :smile:

James, is there a simple "largest P-1 factors" list on your site?[/QUOTE]

Here you go:
[url]http://mersenne.ca/stats.php?showuserstats=*[/url]
FWIW, it would take 3*10^25 TF Ghz-days to find that factor!

In that page it appears that I found a prime factor of M102679 twice, using P-1 and ECM methods. This is a known problem when copying results.txt in the Manual results page. Primenet says that it was found by ECM, while I used P-1. Then I opened the [url]http://mersenne.ca[/url] Web site and dumped my results.txt file there. Now the prime factor appears twice in this Web site.

P-1 found a factor in stage #2, B1=560000, B2=10640000.
UID: Jwb52z/Clay, M60465473 has a factor: 12850552559520705957651673

83.410 bits.

P-1 found a factor in stage #1, B1=560000.
UID: Jwb52z/Clay, M60381703 has a factor: 251637327815644828195129

77.736 bits

P-1 found a factor in stage #2, B1=570000, B2=10687500.
UID: Jwb52z/Clay, M60775031 has a factor: 434496528948485397527849

78.524 bits.

I had some fun this morning when I just saw this, but I had to run so the only thing I had time to do is to approximate the bit level... >170 bits.:fusion:
Then I had to run off to work...

[QUOTE][Sat Feb 09 06:01:04 2013]
P-1 found a factor in stage #2, B1=560000, B2=10640000.
UID: Axelsson/Utveckling, M60070949 has a factor: 91622368695369671284251815722954195372651812038785409
[/QUOTE]almost eight hours later I had time to report my find... what a disappointment, i had found a composite factor. It was just too good to be true and even though I had felt that something was wrong, reality sucks! :ouch2:
Anyhow, my first composite factor from the P-1 method, how common is it with composite factors in P-1?

[QUOTE]Factors found: 1 Processing result: M60070949 has a factor: 91622368695369671284251815722954195372651812038785409 Composite factor 91622368695369671284251815722954195372651812038785409 = 1175315009936832799493321 * 77955584605606208779422907129[/QUOTE]79.96 bit and 95.98 bit, large but not extreme.

My next goal, a triple factor... :big grin:

/Göran

The largest 'non composite' factor found with P-1 are around 100 bits. A 170 bit composite is still a medal contender.
additionnal info
k1(1175315009936832799493321 )= 2^2 * 5 *491 * 377297 * 2640371
k2(77955584605606208779422907129)= 2^2 * 3 * 3719 * 102149 * 115553 * 1231771

meaning *optimal * bound would have been
- if you looked for a stage 1 hit : B1=2640371 B2=2640371
- if you looked for a stage 2 hit : B1=377297 B2=2640371
That would have found the 2 factor and would be faster.
But since we didn't know the factor beforehand, good job.

[QUOTE=firejuggler;328711]The largest 'non composite' factor found with P-1 are around 100 bits. A 170 bit composite is still a medal contender.[/QUOTE]

My largest was 104 bits. I've heard of people finding larger, but they are rare.

Composite factors are rare, but not as rare as 140+ bit prime factors. Any factor with more bits than twice the factored depth is almost certainly composite.

[QUOTE=Mr. P-1;328715]My largest was 104 bits. I've heard of people finding larger, but they are rare.[/QUOTE]There is a 102 bit number in the 100M digit range. M332219539 has 6157103818187609775710294086831 as a factor.

[URL="http://mersenneforum.org/showpost.php?p=319601&postcount=594"]..[/URL]is my largest.